Display means, schemes and arrangements (collectively “Displays”) are generally used in articles, devices, apparatus or systems as means of visual communication to the users, viewers or the general public. In many applications, it is desirable that Displays are provided with colour changing effects or capabilities without requiring complicated electronic control circuitry or delicate display screens. Watches, clocks, personal digital assistants (PDAs), personal computers, ornamental and decorative articles always find such colour variable Displays especially useful and provide additional aesthetic attraction to the users or the public.
For example, digital and analogue timepieces with variable colour Displays are described in U.S. Pat. Nos. 4,647,217 and 4,707,141. In U.S. Pat. No. 5,289,301, the broad concept of using colour modulation liquid crystal displays by adding guest dyes within a liquid crystal material to facilitate a variable colour dial in a wrist-watch has been described. In U.S. Pat. No. 5,636,185, a variable colour display scheme including a driving means for electronically controlling the liquid crystal display segments to change between a first colour, a second colour and intermediate shades of colour by applying prescribed voltages across selected liquid crystal display (“LCD”) segments has also been described.
Displays utilizing a liquid crystal display material to produce the desirable colour variation features, including colour changing, suffer from major drawbacks. Firstly, electrical energy is required to control the liquid crystal display in order to produce the desirable colour changing visual effect. This would be undesirable for devices, for example, wrist-watches, which are expected to operate on a small power source for a pro-longed period of time. Secondly, variation of display colour is usually by electronically controlling a LCD layer interposed between two polarizers as described in U.S. Pat. No. 5,636,185. Such a LCD layer introduces additional thickness which is undesirable for articles or devices of compact and slim designs such as wrist-watches.
U.S. Pat. No. 5,278,542 describes a variable colour display utilizing a matrix of light-emitting dials (LEDs) which requires complicated driving and controlling circuitry as well as a bulky device which is not useful for many applications in which the size and power consumption are critical. U.S. Pat. No. 3,763,647 describes a watch dial which changes colour according to the ambient temperature by the coating of a liquid crystal film on the dial plate. In this application, the colour change cannot be adjusted or changed manually by the user.
Hence, it will be highly desirable and beneficial to provide improved means, schemes and arrangements of variable colour display which alleviate at least some of the shortcomings of the known colour variable Displays. Preferably, such Displays are provided without a complicated or bulky structure with costly components. In addition, it is highly desirable if such colour variable Displays can be controlled manually by the user without complicated adjusting steps or requiring a constant supply of electrical energy to effect or maintain the colour change.